This invention relates generally to fixtures for affixing adhesive backed assemblies onto a support surface.
It is often desirable to secure an “attachment element”, such as a patch or fastener or the like, onto a supporting surface, also referred to as a substrate. For example, holes in the skin of aircraft or boat holes may be repaired by applying a thin patch to close the opening. It is also known to mount threaded fasteners or the like onto a substrate so as to be able to attach additional components to the substrate's surface. In many cases, it is necessary for the attachment to be located on the substrate with high precision.
To this end, various fixtures have been devised for securing an attachment to a substrate. Typically, the fixtures include means for positively urging the attachment to a substrate while an adhesive bonds the attachment in place. Clamps and similar fixture devices have been used to position and hold the attachment in place while the adhesive cures. Unfortunately, many substrates have constructions which will not allow the use of a clamp to secure an attachment in place. Other fixture devices have been proposed which rely on suction cups for holding the fixture in place upon a substrate. However, suction cup devices are limited to being used on substrates having smooth surfaces. Also, suction cup devices can slowly release from a substrate.
To overcome these disadvantages, adhesive backed fixture assemblies have been devised which temporarily adhere to a substrate for providing pressure and for securing the attachment in place while an adhesive cures. For example, FIGS. 1-6 show prior art constructions which are the subject of U.S. Pat. Nos. 4,302,492; 4,338,151; 4,390,576 and 4,822,656. These patents describe one and two piece fixtures having a support member 9 which temporarily secures to a substrate 6 using a pressure sensitive adhesive or the like. The fixtures further include an inner retainer 25 for releasably holding an attachment 3, such as a threaded fastener. The inner retainer is moveable from a first position 8 to a second position 10. In the first position, the adhesive backed attachment is positioned so as to not engage the substrate. Meanwhile, in the second position, the inner retainer is moved inward so as to engage the substrate. For example, U.S. Pat. No. 4,390,576 and FIGS. 1-3 disclose two piece fixtures wherein a resilient ring holds the outer support member in place and exerts a positive force upon the attachment against the substrate. Once the attachment's adhesive is cured, the fixture, including outer support member and inner retainer, are removed leaving only the attachment in place securely affixed to the substrate. Similarly, U.S. Pat. No. 4,822,656 and FIGS. 4-6 illustrate one piece fixtures for securing an attachment to a substrate as the attachment's adhesive cures. Instead of using a resilient ring to urge the attachment against the substrate, the fixture includes a plurality of spokes which project radially inward from the outer support member to engage the inner retainer. Once the inner retainer is moved into its second position, the spokes apply positive pressure to the attachment while the attachment's adhesive cures.
Unfortunately, the adhesive backed fixtures described in the above-identified patents suffer from a significant disadvantage. In particular, persons applying such fixtures and their corresponding attachments to a substrate will often unintentionally place too much pressure upon the inner retainer. This excessive force causes adhesive material between the attachment and substrate to squeeze out from between the respective parts resulting in a weakened joint between the attachment and substrate when the adhesive cures. Unfortunately, the prior art fixtures do not include a means for preventing excessive force upon the inner retainer being transmitted to the attachment.
For example, FIGS. 1-6 show prior art fixture devices for securing an attachment to a substrate. To secure the attachment, a person places force upon the inner retainer 25 until the inner retainer has moved to a second position 10. In the second position, the attachment 3 engages the substrate 6. Unfortunately, when persons place force upon the inner retainer, often they will place excessive force on the retainer causing the adhesive 4 to seep from between the fastener and substrate resulting in a weakened bond. Moreover, as shown in FIGS. 1 and 2, though some fixture devices include a cap 29 for manual manipulation of the fixture, the cap is not constructed so as to engage the outer support member 9. Instead, when the inner retainer is moved to the second position, a space 12 is left remaining between the inner retainer and outer support member. Fixture devices including spokes also have not been devised to include a structure for preventing excessive seepage of the adhesive caused by excessive force upon the inner retainer. Instead, the resiliency of the spokes 53 permits the inner retainer to proceed far beyond the intended second position.
Accordingly, it would be highly desirable to provide a fixture which ensures that proper force is applied to an attachment as it adheres to a substrate.
Furthermore, it would be highly desirable to provide an improved fixture which ensures that excessive pressure is not transmitted to the attachment when the inner retainer is moved from its first non-engaging position to its second engaging position.